Diagnostic method for a compressor recirculation valve

ABSTRACT

Methods are provided for identifying degradation in components of a compressor bypass valve (CBV). One method comprises commanding a periodic signal to the CBV and indicating degradation of a throttle of the CBV based on changes in pressure at an inlet of an intake throttle in response to the periodic signal.

FIELD

The present application relates to methods for diagnosing degradation ofa throttle in a compressor recirculation valve coupled across an intakecompressor in an internal combustion engine.

BACKGROUND AND SUMMARY

Engine systems may be configured with boosting devices, such asturbochargers or superchargers, for providing a boosted aircharge andimproving peak power outputs. The use of a compressor allows a smallerdisplacement engine to provide as much power as a larger displacementengine, but with additional fuel economy benefits. However, compressorsare prone to surge. For example, when an operator tips-out of anaccelerator pedal, an engine intake throttle closes, leading to reducedforward flow through the compressor, and a potential for surge. Surgecan lead to noise, vibration, and harshness (NVH) issues such asundesirable noise from the engine intake system. In extreme cases, surgemay result in compressor damage. To address compressor surge, enginesystems may include a compressor recirculation valve (CRV) coupledacross the compressor to enable rapid decaying of boost pressure. TheCRV may recirculate compressed air from the compressor outlet to thecompressor inlet allowing a decrease in pressure at the compressoroutlet.

The CRV may comprise a throttle and a position sensor for indicating achange in a position of the throttle of the CRV. As such, the CRV maydegrade with use over time. For example, the throttle of the CRV may bestuck at a given position and may not move when commanded. In oneexample, the throttle may be stuck in a fully open position.Alternatively, the throttle may be lodged in a fully closed position. Inyet another example, the throttle may be stuck at a position in-betweenthe fully closed and fully open positions. An example approach to verifyif the CRV is stuck in an open position is shown by Wegener et al. inU.S. Pat. No. 7,926,335. Herein, changes in charging pressure inresponse to a triggering of the CRV are analyzed. Specifically, the CRVmay be diagnosed to be stuck in a mostly open position if the chargingpressure downstream of the intake compressor does not increase asexpected when the CRV is triggered to a closed position. U.S. Pat. No.7,926,335 primarily identifies a CRV that is stuck in an open or mostlyopen position.

The inventors herein have identified a potential issue with the aboveapproach. As an example, variations in charging pressure may be due tofactors other than a change in position of the CRV throttle. Forexample, charging pressure may fluctuate due to modifications to pedalposition (e.g. accelerator pedal), changes in gear, spark timingchanges, etc. Noise from these and other parameters may influencecharging pressure. Accordingly, variations in charging pressure inresponse to a triggering of the CRV cannot be exclusively ascribed to achange in CRV position.

The inventors herein have recognized the above issue and identified anapproach to at least partly address the issue. In one example, a methodfor a boosted engine comprises commanding a periodic signal command to acompressor bypass valve (CBV), and indicating degradation of a throttleof the CBV based on changes in pressure at an inlet of an intakethrottle in response to a the periodic signal command. In this way, CRVthrottle degradation may be specifically identified.

For example, an engine system may include a compressor having acompressor recirculation passage coupling an outlet of the compressor tothe compressor inlet. In alternate embodiments, the recirculation pathmay couple an outlet of a charge air cooler to the compressor inlet.Flow through the recirculation path may be controlled via a compressorrecirculation valve (CRV). The CRV may be a continuously variablecompressor recirculation valve (CCRV). An engine controller may beconfigured to adjust a position of the CRV based on changes in airflowthrough an intake throttle so as to reduce compressor surge. Further,the engine controller may receive feedback regarding changes in throttleinlet pressure (TIP) from a throttle inlet pressure sensor locatedupstream of the intake throttle and downstream of the compressor. Inorder to determine if the CRV is degraded (e.g. stuck in a givenposition), TIP may be measured in response to a commanded change inposition of the CRV. To ensure that TIP readings are minimally affectedby noise factors, the command may include a periodic signal. In oneexample, the periodic signal may be a square waveform signal. Ifvariations in TIP substantially correspond to the periodicity of thecommanded periodic signal, the CRV may not be degraded (e.g. not stuck).However, if changes in TIP do not substantially match the periodicpattern of the commanded periodic signal, the CRV may be diagnosed to bedegraded.

In this way, CRV degradation may be determined in a more reliablemanner. By commanding a periodic signal with a specific periodicity,influence of noise factors on throttle inlet pressure (or chargingpressure) may be reduced. Further, a more accurate determination ofdegradation in the CRV, particularly degradation of CRV throttle, may berealized. Further still, by isolating the degradation to a specificcomponent of the CRV, diagnosis and repair expenses may be reduced.Overall, maintenance of the engine may be enhanced.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an example embodiment of a boosted engine systemincluding a compressor recirculation valve (CRV).

FIG. 2 portrays a high level flow chart illustrating a routine todetermine if degradation of the CRV is present.

FIG. 3 shows a high level flow chart illustrating a routine duringengine operation to differentiate between degradation of a throttle ofthe CRV and degradation of a position sensor of the CRV.

FIG. 4 presents a high level flow chart comparing example correctiveadjustments in response to the determination of degradation in thethrottle of the CRV with those in response to the determination ofdegradation of the position sensor of the CRV.

FIG. 5 is a high level flow chart illustrating a routine that may beimplemented via operator input to determine if CRV degradation is due todegradation of the position sensor or the throttle of the CRV.

FIG. 6 depicts a high level flow chart for establishing degradation inthe CRV while reducing noise factors that may affect throttle inletpressure.

FIG. 7 demonstrates an example operation for differentiating betweendegradation in the position sensor of the CRV and degradation of thethrottle of the CRV.

FIG. 8 portrays an example operation for diagnosing the CRV throttlebased on throttle inlet pressure (TIP) while reducing noise from otherfactors that may affect TIP readings.

DETAILED DESCRIPTION

The following description relates to systems and methods for diagnosingdegradation in a compressor recirculation valve (CRV) in a boostedengine system, such as the system of FIG. 1. A controller may beconfigured to perform a control routine, such as the routine of FIG. 2,to determine if the CRV is degraded. As such, the CRV may include athrottle whose position may be adjusted by the controller based onengine conditions. The CRV may also comprise a position sensor forconfirming the change in position of the throttle of the CRV in responseto a command by the controller. The controller may differentiate betweendegradation of the throttle of the CRV and degradation of the positionsensor of the CRV by performing a control routine, such as the routineof FIG. 3, during engine operation. Degradation of the throttle of theCRV may be distinguished from degradation of the position sensor of theCRV based on each of a throttle inlet pressure, and a commanded positionof the throttle of the CRV. Additionally, an output of the positionsensor in response to the commanded position of the throttle of the CRVmay be used to differentiate between degradation of the throttle anddegradation of the position sensor of the CRV (FIG. 7). In response tothe determination of CRV degradation, various engine parameters andactuators may be adjusted to enable desired engine operation (FIG. 4).Additional confirmation of degradation in the position sensor orthrottle of the CRV may be provided by activating a routine such as thatshown in FIG. 5, via operator input. Further still, the controller maybe configured to perform a control routine, such as the routine in FIG.6, to ensure that changes in throttle inlet pressure are due toadjustments in the position of the CRV. Specifically, degradation of theCRV throttle may be determined by commanding a periodic signal to theCRV and observing variations in throttle inlet pressure (FIG. 8). Inthis way, degradation of the CRV throttle may be isolated fromdegradation of the position sensor of the CRV, and CRV maintenance maybe enhanced.

FIG. 1 shows a schematic depiction of an example turbocharged enginesystem 100 including a multi-cylinder internal combustion engine 10 andtwin turbochargers 120 and 130. As one non-limiting example, enginesystem 100 can be included as part of a propulsion system for apassenger vehicle. Engine system 100 can receive intake air via intakepassage 140. Intake passage 140 can include an air filter 156. Enginesystem 100 may be a split-engine system wherein intake passage 140 isbranched downstream of air filter 156 into first branch and secondbranch intake passages, each including a turbocharger compressor. In theresulting configuration, at least a portion of intake air is directed tocompressor 122 of turbocharger 120 via a first branch intake passage 142and at least another portion of the intake air is directed to compressor132 of turbocharger 130 via a second branch intake passage 144 of theintake passage 140.

The first portion of the total intake air that is compressed bycompressor 122 may be supplied to intake manifold 160 via a firstparallel branched intake passage 146. In this way, intake passages 142and 146 form a first combined branch of the engine's air intake system.Similarly, a second portion of the total intake air can be compressedvia compressor 132 and may be supplied to intake manifold 160 via secondparallel branched intake passage 148. Thus, intake passages 144 and 148form a second combined branch of the engine's air intake system. Asshown in FIG. 1, intake air from intake passages 146 and 148 can berecombined via a common intake passage 149 before reaching intakemanifold 160, where the intake air may be provided to the engine.

In some examples, intake manifold 160 may include an intake manifoldpressure sensor 182 for estimating a manifold pressure (MAP) and/or anintake manifold temperature sensor 183 for estimating a manifold airtemperature (MCT), each communicating with controller 12. Common intakepassage 149 may include a charge air cooler 154 and an intake throttle158. The position of intake throttle 158 can be adjusted via a throttleactuator (not shown) communicatively coupled to controller 12. Athrottle inlet pressure (TIP) sensor 173 may be coupled to common intakepassage 149 at a location upstream of intake throttle 158 and downstreamof air cooler 154. Further, TIP sensor 173 may be located downstream ofcompressors 122 and 132. Throttle inlet pressure, also referred to asthe boost pressure or charging pressure, may be estimated by TIP sensor173.

A compressor recirculation passage 150 may be provided for compressorsurge control. Specifically, to reduce compressor surge, such as on adriver tip-out, boost pressure may be dumped from the intake manifold,from downstream of air cooler 154 and upstream of intake throttle 158,to intake passage 140 (in particular, downstream of air filter 156 andupstream of the junction of intake passages 142 and 144). By flowingboosted air from upstream of an intake throttle inlet to upstream of thecompressor inlets, boost pressure may be rapidly reduced, expeditingboost control.

Flow through compressor recirculation passage 150 may be regulated byadjusting the position of compressor recirculation valve 152 (CRV 152)positioned therein. CRV 152 may also be termed a compressor surge valve,a compressor bypass valve (CBV), a diverter valve, etc. In the depictedexample, compressor recirculation valve 152 may be a continuouslyvariable valve whose position can be adjusted to a fully open position,a fully closed position, or any position there-between. Thus, compressorrecirculation valve 152 may also be referred to herein as a continuouslyvariable compressor recirculation valve, or CCRV. In the depictedexample, CCRV 152 is configured as a throttle valve, although in otherembodiments, the CCRV may be configured differently (e.g., as a poppetvalve). Accordingly, CCRV 152 may include a throttle (e.g. as a throttleplate) as well as a position sensor for communicating a change inposition of the throttle of the CCRV to the controller 12. The positionsensor for the throttle of the CCRV (or simply CRV) may also be referredto as throttle position sensor (TPS) or CCRV throttle position sensor.It will be appreciated that while the CCRV is shown configured for a V-6twin turbocharged engine in FIG. 1, the CCRV may be similarly applied inother engine configurations, such as applied to I-3, I-4, V-8, and otherengine configurations with one or multiple turbochargers.

In an alternate configuration, the compressor recirculation passage maybe located such that compressed air flows from upstream of air cooler154 to a location upstream of compressors 122 and 132. In anotherconfiguration, there may be two recirculation paths, each with arecirculation valve, each located such that compressed air travels fromthe compressor exit to the compressor inlet. It will also be appreciatedthat the methods described herein may be applied to a compressorrecirculation valve that is not continuously variable.

During nominal engine operating conditions, the continuously variablecompressor recirculation valve 152 may be kept nominally closed, ornearly closed. In such a position, the valve may be operating with knownor negligible leakage. Then, in response to surge, an opening of theCCRV 152 may be increased. In some embodiments, one or more sensors maybe coupled in compressor recirculation passage 150 to determine the massof recirculated flow delivered from the throttle inlet to the intakepassage. The various sensors may include, for example, pressure,temperature, and/or flow sensors.

In alternate embodiments, the compressor recirculation valve may beconfigured as a two-position valve adjustable to one of a fully closedand a fully open position. However, boost regulation may be improved byusing a CCRV. In addition, by coordinating the operation of the CCRVwith those of a wastegate, boost response and surge margins can beimproved. As such, the impact of the opening or closing of the CCRV 152on boost pressure may be substantially immediate. This allows rapidboost and surge control.

Engine 10 may include a plurality of cylinders 14. In the depictedexample, engine 10 includes six cylinders arranged in a V-configuration.Specifically, the six cylinders are arranged on two banks, first bank 13and second bank 18, with each bank including three cylinders. Inalternate examples, engine 10 can include two or more cylinders such as4, 5, 8, 10 or more cylinders. These various cylinders can be equallydivided and arranged in alternate configurations, such as V, in-line,boxed, etc. Each cylinder 14 may be configured with a fuel injector 166.In the depicted example, fuel injector 166 is a direct in-cylinderinjector. However, in other examples, fuel injector 166 can beconfigured as a port based fuel injector.

Intake air supplied to each cylinder 14 (herein, also referred to ascombustion chamber 14) via common intake passage 149 may be used forfuel combustion and products of combustion may then be exhausted viabank-specific parallel exhaust passages. In the depicted example, firstbank 13 of cylinders of engine 10 can exhaust products of combustion viaa first parallel exhaust passage 17 and second bank 18 of cylinders canexhaust products of combustion via a second parallel exhaust passage 19.Each of the first and second parallel exhaust passages 17 and 19 mayfurther include a turbocharger turbine. Specifically, products ofcombustion that are exhausted via exhaust passage 17 can be directedthrough exhaust turbine 124 of turbocharger 120, which in turn canprovide mechanical work to compressor 122 via shaft 126 in order toprovide compression to the intake air. Alternatively, some or all of theexhaust gases flowing through exhaust passage 17 can bypass exhaustturbine 124 via turbine bypass passage 123 as controlled by wastegate128. Similarly, products of combustion that are exhausted via exhaustpassage 19 can be directed through exhaust turbine 134 of turbocharger130, which in turn can provide mechanical work to compressor 132 viashaft 136 in order to provide compression to intake air flowing throughthe second branch of intake passage 144 of the engine's intake system.Alternatively, some or all of the exhaust gas flowing through exhaustpassage 19 can bypass exhaust turbine 134 via turbine bypass passage 133as controlled by wastegate 138.

In some examples, exhaust turbines 124 and 134 may be configured asvariable geometry turbines, wherein controller 12 may adjust theposition of the turbine impeller blades (or vanes) to vary the level ofenergy that is obtained from the exhaust gas flow and imparted to theirrespective compressor. Alternatively, exhaust turbines 124 and 134 maybe configured as variable nozzle turbines, wherein controller 12 mayadjust the position of the turbine nozzle to vary the level of energythat is obtained from the exhaust gas flow and imparted to theirrespective compressor. For example, the control system can be configuredto independently vary the vane or nozzle position of the exhaustturbines 124 and 134 via respective actuators.

Exhaust gases in first parallel exhaust passage 17 may be directed tothe atmosphere via branched parallel exhaust passage 170 while exhaustgases in second parallel exhaust passage 19 may be directed to theatmosphere via branched parallel exhaust passage 180. Exhaust passages170 and 180 may include one or more exhaust after-treatment devices,such as a catalyst, and one or more exhaust gas sensors (not shown).

In some embodiments, engine 10 may further include one or more exhaustgas recirculation (EGR) passages for recirculating at least a portion ofexhaust gas from first and second parallel exhaust passages 17 and 19and/or first and second parallel branched exhaust passages 170 and 180,to first branch and second branch intake passages 142 and 144, and/orfirst and second parallel branched intake passages 146 and 148 or intakemanifold 160. These may include high-pressure EGR loops for providinghigh-pressure EGR (HP-EGR) and low-pressure EGR-loops for providinglow-pressure EGR (LP-EGR). When included, HP-EGR may be provided in theabsence of boost provided by turbochargers 120, 130, while LP-EGR may beprovided in the presence of turbocharger boost and/or when exhaust gastemperature is above a threshold. In still other examples, both HP-EGRand LP-EGR may be provided simultaneously. The low-pressure EGR loopsmay recirculate at least some exhaust gas from each of the branchedparallel exhaust passages, downstream of the exhaust turbine, to thecorresponding branch of intake passage, upstream of the compressor. Eachof the LP-EGR loops may have corresponding LP-EGR valves, forcontrolling exhaust flow through the LP-EGR loop, as well as respectivecharge air coolers for lowering a temperature of exhaust gasrecirculated to the engine intake. The high-pressure EGR loops mayrecirculate at least some exhaust gas from each of the parallel exhaustpassages, upstream of the exhaust turbine, to the corresponding parallelintake passage, downstream of the compressor. As shown, high-pressureEGR loop 177 can recirculate a portion of exhaust gas from firstparallel exhaust passage 17 to first parallel branched intake passage146. Similarly, high-pressure EGR loop 197 may recirculate at least someexhaust gas from second parallel exhaust passage 19 to second parallelbranched intake passage 148. EGR flow through the HP-EGR loops may becontrolled via respective HP-EGR valves and HP-EGR charge air coolers(not shown). Thus, EGR flow through high-pressure EGR loop 197 may becontrolled by HP-EGR valve 195, while EGR flow through high-pressure EGRloop 177 is controlled by HP-EGR valve 175.

The position of intake and exhaust valves of each cylinder 14 may beregulated via hydraulically actuated lifters coupled to valve pushrods,or via a cam profile switching mechanism in which cam lobes are used. Inthis example, at least the intake valves of each cylinder 14 may becontrolled by cam actuation using a cam actuation system. Specifically,the intake valve cam actuation system 25 may include one or more camsand may utilize variable cam timing or lift for intake and/or exhaustvalves. In alternative embodiments, the intake valves may be controlledby electric valve actuation. Similarly, the exhaust valves may becontrolled by cam actuation systems or electric valve actuation. Camactuation systems may include one or more cams mounted on one or morecamshafts and may utilize one or more of cam profile switching (CPS),variable cam timing (VCT), variable valve timing (VVT) and/or variablevalve lift (VVL) systems that may be operated by controller 12 to varyvalve operation.

Engine system 100 may be controlled at least partially by a controlsystem 15 including controller 12 and by input from a vehicle operator190 via an input device 192. In this example, input device 192 includesan accelerator pedal and a pedal position sensor 194 for generating aproportional pedal position signal PP.

Control system 15 is shown receiving information from a plurality ofsensors 16 (various examples of which are described herein) and sendingcontrol signals to a plurality of actuators 81. As one example, sensors16 may include TIP sensor 173, a humidity sensor, MAP sensor 182, andMCT sensor 183. In some examples, a throttle inlet temperature sensorfor estimating a throttle air temperature (TCT) may be located upstreamof intake throttle 158. In other examples, one or more of the EGRpassages may include pressure, temperature, and air-to-fuel ratiosensors, for determining EGR flow characteristics. As another example,actuators 81 may include CCRV 152, fuel injector 166, HP-EGR valves 175and 195, LP-EGR valves (not shown), intake throttle 158, and wastegates128, 138. Other actuators, such as a variety of additional valves andthrottles, may be coupled to various locations in engine system 100.Controller 12 may receive input data from the various sensors, processthe input data, and trigger the actuators in response to the processedinput data based on instruction or code programmed therein correspondingto one or more routines. Example control routines are described hereinwith regard to FIGS. 2-6.

The present disclosure describes methods to distinguish betweendegradation of a throttle of a CCRV and degradation of a position sensorof the CCRV. It will be noted that throughout the disclosure CRV andCCRV may be used interchangeably to represent the compressorrecirculation valve which may be continuously variable. In one example,the throttle of the CCRV may be degraded and may be stuck in an open (ormostly open) position. Herein, boost created by the compressor(s) may becontinuously bled off impacting torque delivery and drivability. Inanother example, the throttle of the CCRV may be degraded and stuck in aclosed (or mostly closed) position. Accordingly, the CCRV may not reducecompressor surge, as desired, which can lead to noise, vibration andharshness (NVH) issues as well as compressor degradation. In yet anotherexample, the position sensor of the CCRV may be degraded. For example,wiring and/or processing circuitry within the position sensor may bedegraded. Thus, the position sensor may provide incorrect indications ofthrottle position of the CCRV. Further, accurate control of the positionof the throttle of the CCRV may not be possible. Accordingly,identification of degradation in specific components may be advantageousfor engine control as well as for reducing repair costs.

As a first step, the controller in the vehicle may identify CCRVdegradation when the position sensor of the CCRV does not indicate anexpected change in position of the CCRV throttle in response to acommanded change in position of the CCRV throttle. CCRV degradation mayinclude one or more of degradation of the throttle of the CCRV anddegradation of the position sensor of the CCRV. Based on engineconditions, the controller may then identify which of the components ofthe CCRV may be degraded. Herein, a distinction may be based upon eachof a change in throttle inlet pressure (TIP) as measured by a TIPsensor, and a commanded change in position of the CCRV throttle.Further, the output of the position sensor of the CCRV throttle may beused in addition to TIP readings and the commanded change in position ofthe CCRV throttle to identify component specific degradation in theCCRV.

If engine conditions cannot distinguish between throttle and positionsensor degradation in the CCRV, component specific degradation may bedetected via operator input. Herein, the operator may initiate adiagnostic routine wherein the controller may command a change inposition of the CCRV throttle, measure a corresponding change (or lackof change) in TIP, and determine which specific component of the CCRV isdegraded. Additionally or alternatively, CCRV throttle degradation mayalso be determined by commanding a periodic signal to the CCRV throttlevia operator input. As such, this diagnostic may also ensure that theTIP as estimated by the TIP sensor is not affected by noise from otherengine parameters. The periodic signal may be a square waveform with aperiod based on turbo-dynamics. Resulting changes in TIP may be measuredand CCRV throttle degradation may be indicated if the changes in TIP donot substantially correspond to the frequency and periodicity of thecommanded signal. If changes in TIP substantially correspond to theperiodicity of the commanded signal, the throttle of the CCRV may bedetermined to be robust.

Further details will be described in reference to routines shown inFIGS. 2-6 below. It will be noted that routines 200, 300, 400, 500, and600 refer to the position sensor of the CCRV as TPS (throttle positionsensor) wherein the TPS output indicates a position of the CCRV throttleand/or indicates changes in the position of the CCRV throttle. Further,a commanded signal or position change to the CCRV indicates a commandedchange in position of the CCRV throttle. It will also be noted thatroutines 200, 300, 400, 500, and 600 refer to the CRV as CCRV indicatingthat the compressor recirculation valve is a continuously variablecompressor recirculation valve, as in FIG. 1. As such, the CCRV may beadjusted to a fully open position, a fully closed position, or anyposition in-between the fully closed and fully open positions.

FIG. 2 presents an example routine 200 for determining if CRV (or CCRV)degradation is present in a boosted engine, such as the engine system ofFIG. 1. Specifically, CRV degradation may be likely when a positionsensor of the CRV does not indicate an expected change in position ofthe CRV throttle in response to a commanded change in position.

At 202, routine 200 may estimate and/or measure one or more engineoperating conditions. Engine operating conditions may include engineload, boost pressure (or TIP), engine speed, torque demand, air-fuelratio, a duration of engine operation, exhaust temperature, etc. Forexample, TIP may be estimated to determine if surge conditions may bepresent. In another example, torque demand and boost may be estimated todetermine if turbocharger spool-up is desired.

At 204, routine 200 may determine if a change in CRV (or CCRV) positionis desired. As an example, if surge conditions are present, the CCRV maybe adjusted from a mostly closed position to an open (or mostly open)position. In another example, if turbocharger spool-up is desired, theCCRV may be adjusted to a more closed (or fully closed) position from amostly open position. If it is determined at 204 that a change in CCRVposition is not desired, routine 200 may not continue and may end. Onthe other hand, if a change in CCRV position is demanded, at 206,routine 200 commands the desired change in CRV position. In one example,to reduce surge, the CCRV may be commanded to a more open position. Inanother example, the CCRV may be commanded to a more closed position forenabling an increase in boost levels.

At 208, routine 200 determines if the position sensor of the CCRVthrottle indicates the expected change in position. In one example, ifthe CCRV throttle has been commanded to a mostly open position from amostly closed position, the position sensor may signal the correspondingchange in position of the CCRV throttle responsive to the command.Likewise, in another example, if the CCRV throttle is commanded to amostly closed position from a fully open position, the position sensormay indicate the corresponding change in position of the CCRV throttle.If yes, routine 200 proceeds to 210 to not diagnose the CCRV fordegradation of either the position sensor or the CCRV throttle. Routine200 then ends. If at 208 the position sensor does not signal theexpected change in position, routine 200 continues to 212 to determinedegradation of the CCRV. At 214, further diagnosis of the CCRV may beinitiated by activating routine 300 of FIG. 3 to identify if thedegradation of the CCRV includes degradation of the position sensorand/or degradation of the CCRV throttle. Alternatively, in someembodiments, routine 200 may activate a diagnostic code indicating CCRVdegradation and request activation of routine 500 of FIG. 5 via operatorinput after 212. For example, routine 500 may be activated by operatorinput at a service center, dealership, or other similar locationsoffering repair. Routine 200 then ends.

When CCRV degradation is determined, the controller may attempt to useexisting engine conditions with resulting actuator commands (e.g.commands to CCRV) to differentiate between degradation of the throttleof the CCRV and degradation of the position sensor of the CCRV (viaroutine 300 of FIG. 3). This diagnosis may be further confirmed byoperator input via routines 500 (of FIG. 5) and 600 (of FIG. 6).Routines 500 and 600 may be utilized additionally or alternatively toroutine 300. If the existing engine conditions and resulting actuatorcommands cannot isolate component specific degradation in the CCRV,further diagnoses may be conducted via operator input as shown inroutines 500 (of FIG. 5) and 600 (of FIG. 6).

Turning now to FIG. 3, it depicts routine 300 for identifying componentspecific degradation in the CCRV during engine operation. Specifically,the routine may diagnose for degradation of the position sensor (TPS)and/or CCRV throttle based on TIP, the output of the position sensor,and commanded changes to the CCRV. It will be appreciated that routine300 may be performed without operator input or manual commands when theengine is operational.

At 302, routine 300 monitors commands to the CCRV, resulting changes inTIP as communicated from the TIP sensor (e.g. TIP sensor 173 of FIG. 1),and corresponding readings from the position sensor, if any. At 304,routine 300 determines if the CCRV has been commanded closed, and ifthere is a resulting increase in TIP while the output of the positionsensor indicates that the CCRV is open. For example, the CCRV may becommanded closed if a tip-in event is occurring to enable higher levelsof boost. In one example, the CCRV throttle may be commanded to a fullyclosed position from a fully open position. In another example, the CCRVthrottle may be commanded to a fully closed position from a mostly openposition. In yet another example, the CCRV throttle may be commanded toa mostly closed position from a mostly open position. If an increase inTIP is measured by the TIP sensor, the CCRV throttle may be in itscommanded closed position. As such, the CCRV throttle may be in a fullyclosed position such that no airflow or nominal airflow may occurthrough compressor recirculation passage 150 in FIG. 1. However, if theTPS sensor output does not indicate the corresponding change in positionof the CCRV throttle, routine 300 may continue to 306 to determine alikelihood of degradation in the position sensor of the CCRV. Thus,routine 300 continues to 306 if the CCRV has been commanded closed witha resulting increase in TIP while the output of the position sensorindicates that the CCRV is open. Herein, the TPS may indicate that theCCRV throttle is at an open position, which may be the initial positionof the CCRV throttle before receiving the command to close from thecontroller at 304.

At 306, routine 300 may activate routine 400 of FIG. 4 to provideremedial action in response to the determination of likelihood ofdegradation of the position sensor of the CCRV. For example, thedetermination of degradation of the position sensor may be followed bydeactivating the CCRV. Consequently, boost and surge conditions may becontrolled, in one example, by adjusting the wastegate coupled acrossthe exhaust turbine of the turbocharger. In other examples, one or moreof the intake throttle, variable cam timing, and turbocharger vanes maybe adjusted in response to the deactivation of the CRV. Next, at 308,the determination of likelihood of TPS degradation may be furtherconfirmed (optionally) by routine 500 of FIG. 5. As such, the routine ofFIG. 5 may be activated via operator input, for example, at an autorepair shop. Further, at 310, in response to the determination of TPSdegradation, a diagnostic code may be set indicating the likelihood ofTPS degradation and a malfunction indicator lamp (MIL) may be activatedto notify the vehicle operator.

Returning to 304, if routine 300 determines that the CCRV is notcommanded closed without a resulting increase in TIP while the output ofthe position sensor indicates that the CCRV is open, routine 300progresses to 312 to confirm if the CCRV is commanded open with aresulting decrease in TIP while the TPS output indicates that the CCRVis closed. For example, the CCRV may be commanded open if surgeconditions are indicated. In one example, the CCRV throttle may becommanded to a fully open position from a fully closed position. Inanother example, the CCRV throttle may be commanded to a fully openposition from a mostly closed position. In yet another example, the CCRVthrottle may be commanded to a mostly open position from a partly openposition. If a decrease in TIP is measured by the TIP sensor, the CCRVthrottle may be in its commanded open position. Herein, if the TPSoutput indicates that the CCRV throttle is in a closed position (ormostly closed position), routine 300 continues to 306 to determine alikelihood of degradation in the position sensor of the CCRV. Thus,routine 300 may proceed to 306 if the CCRV has been commanded open witha resulting increase in TIP while the output of the position sensorindicates that the CCRV is open. The TPS may indicate that the CCRVthrottle is at a closed position, which may be the initial position ofthe CCRV throttle before receiving the command to open from thecontroller at 312.

At 306, as explained earlier, routine 400 of FIG. 4 may be actuated forcorrective action in response to the determination of likelihood ofdegradation of the position sensor of the CRV. At 308, the determinationof likelihood of TPS degradation may be further confirmed (optionally)by routine 500 of FIG. 5. Further, at 310, in response to thedetermination of TPS degradation, a diagnostic code may be setindicating the likelihood of TPS degradation and the MIL may beactivated to notify the vehicle operator.

Returning to 312, if it is determined that the CCRV is not commandedopen, routine 300 proceeds to 314 to confirm if an existing enginecondition demands a closure of the CCRV. For example, the CCRV may becommanded to the fully closed position. Further, at 314, it may beconfirmed if measured TIP is not substantially equal to an expected peakTIP, and if the TPS output indicates that the CCRV throttle is at anopen (or mostly open) position. As such, for a given model of an engineincluding a given size of CCRV, known restrictions in the path to theCCRV, specific design of each of the intake compressor(s) and exhaustturbine(s), specific engine size and design, and based on engineoperating characteristics such as spark timing, intake throttle angle,fuel type, etc., a peak obtainable TIP may be known. Accordingly, if theexpected TIP (e.g. peak TIP) does not match the measured TIP when theCCRV is commanded closed, while the TPS indicates that the CCRV throttleis at an open (or mostly open) position, the CCRV throttle may bedetermined to be degraded. Routine 300 continues to 316 if the CCRV hasbeen commanded closed, and if the resulting increase in TIP is notequivalent to an expected peak TIP while the output of the positionsensor indicates that the CCRV is open.

At 316, routine 300 determines a likelihood of degradation of the CCRVthrottle. Specifically, CCRV throttle may be stuck in an open (or mostlyopen) position. If the CCRV throttle is lodged in an open position (ormostly open position), sufficient boost may not be developed andcharging pressure at the inlet of the intake throttle may be lower thanexpected. Further, based on the determination of degradation of the CCRVthrottle (e.g. stuck open), various corrective actions may be taken at322 based on routine 400 of FIG. 4. Next, at 324, further confirmationof the degradation of the CCRV throttle may be performed via operatorinput. This may be an optional activation of either routine 500 of FIG.5 or routine 600 of FIG. 6. At 326, a respective diagnostic codeindicating the degraded throttle (e.g. throttle stuck open) may be setand the MIL may be activated. Routine 300 may then end.

If a closure of the CCRV is not commanded at 314, routine 300 continuesto 318 to confirm if an existing engine condition demands an opening ofthe CCRV. Herein, the CCRV throttle may be commanded to a fully open (ormostly open) position from a closed (or mostly closed position). At 318,it may also be determined if the commanded opening of the CCRV does notproduce a decrease in TIP and the TPS indicates that the CCRV throttleis closed (or mostly closed). For example, if the CCRV throttle does notchange position as commanded to a more open position, TIP may remain ata higher level than desired. If the TPS indicates that the throttle ofthe CCRV has not moved, and remains in a closed (or mostly closed)position, the CCRV throttle may be degraded. Specifically, the CCRVthrottle may be stuck in a closed (or mostly closed) position.Therefore, if a decrease in TIP is not measured by the TIP sensor inresponse to the commanded opening of the CCRV while the TPS indicatesthat the CCRV throttle is in the closed (or mostly closed) position,routine 300 continues to 320 to determine the likelihood of degradationof the CCRV throttle (e.g. stuck closed). Further, at 322, acorresponding corrective action may be initiated according to routine400 of FIG. 4. Next, at 324, further confirmation of the degradation ofthe CRV throttle may be performed via operator input. This may be anoptional activation of either routine 500 of FIG. 5 or routine 600 ofFIG. 6. At 326, a respective diagnostic code indicating the degradedthrottle (e.g. throttle stuck closed) may be set and the MIL may beactivated. Routine 300 may then end.

Returning to 318, if the CRV is not commanded open (and a resultingchange in TIP is not observed while TPS indicates that the CRV throttleis closed), routine 300 progresses to 328 to wait and perform diagnosticroutine 500 via operator input. In addition, at 330, diagnostic code “M”may be set and the MIL may be activated. Herein, the diagnostic code “M”may indicate that further diagnosis via operator input is neededwhereupon diagnostic routine 500 may be activated at a later time.

Thus, an example method for a boosted engine may comprisedifferentiating between degradation of a throttle of a compressorrecirculation valve (CRV) and a position sensor of the CRV based on eachof a throttle inlet pressure and commanded position of the throttle ofthe CRV. The CRV may be a continuously variable compressor recirculationvalve (CCRV). The differentiating between degradation of the throttle ofthe CRV and the position sensor of the CRV may also be based on anoutput from the position sensor of the CRV in response to the commandedposition of the throttle of the CRV. Further, the throttle inletpressure may be measured upstream of an intake throttle positioned in anintake passage of the boosted engine. The method may further compriseindicating degradation of the position sensor based on a change inthrottle inlet pressure responsive to a commanded change in a positionof the throttle of the CRV and a lack of change in a response of theposition sensor responsive to the commanded change in the position ofthe throttle of the CRV (as at either 304 or 312 of routine 300). Inresponse to the indicating of degradation of the position sensor of theCRV, the method may include deactivating the CRV in response to theindicating of degradation of the position sensor of the CRV. Further, inresponse to the deactivating of the CRV, the method may compriseadjusting one or more of a wastegate, an intake throttle, and variablecam timing. The method may also include indicating degradation of thethrottle of the CRV based on a lack of change in a response of theposition sensor responsive to a commanded change in a position of thethrottle of the CRV and a lack of change in throttle inlet pressureresponsive to the commanded change in the position of the throttle ofthe CRV. Herein, degradation of the throttle of the CRV may include oneof the throttle being stuck open and the throttle being stuck closed.Alternatively, or additionally, degradation of the throttle may includeone or more of the throttle being partially stuck open and the throttlebeing partially stuck closed.

Another example method may comprise actuating a continuously variablecompressor recirculation valve (CCRV), indicating degradation of theCCRV based on feedback from a position sensor of the CCRV indicating athrottle of the CCRV did not change position upon actuation, anddifferentiating between degradation of the throttle of the CCRV and theposition sensor of the CCRV. The differentiating between degradation ofthe throttle of the CCRV and the position sensor of the CCRV may bebased on throttle inlet pressure, the throttle inlet pressure measuredby a sensor positioned upstream of an intake throttle and downstream ofan intake compressor. The differentiating between degradation of thethrottle of the CCRV and the position sensor of the CCRV may be furtherbased on a commanded change in CCRV position, an expected change inthrottle inlet pressure, and feedback from the position sensor of theCCRV.

For example, the method may comprise indicating degradation of theposition sensor based on an increase in throttle inlet pressure inresponse to the CCRV being commanded to a closed position and feedbackfrom the position sensor indicating the CCRV is open. In anotherexample, the method may also include indicating degradation of theposition sensor based on a decrease in throttle inlet pressure inresponse to the CCRV being commanded to an open position and feedbackfrom the position sensor indicating the CCRV is closed. In yet anotherexample, the method may further comprise indicating degradation of thethrottle of the CCRV based on a lack of change in throttle inletpressure in response to the CCRV being commanded to a closed positionand feedback from the position sensor indicating the CCRV is open.Alternatively, the increase in throttle inlet pressure may not beequivalent to an expected rise in throttle inlet pressure in response tothe CCRV being commanded to a closed position, and the position sensormay indicate that the CCRV is open. In an additional example, the methodmay indicate degradation of the throttle of the CCRV based on a lack ofchange in throttle inlet pressure in response to the CCRV beingcommanded to an open position and feedback from the position sensorindicating the CCRV is closed. Herein, the throttle inlet pressure maynot decrease as expected when the CCRV is commanded to the openposition.

Turning now to FIG. 4, it depicts example routine 400 demonstratingvarious adjustments that may be performed based on determination ofdegradation of the position sensor (TPS) of the CCRV throttle ordegradation of the CCRV throttle (e.g. throttle stuck open or closed).Specifically, desired boost levels may be attained and surge control maybe performed by adjusting positions of the wastegate, the intakethrottle, valve timings, etc. It will be appreciated that routine 400may be activated only after a determination of either TPS degradation orCCRV throttle degradation in routine 300 of FIG. 3.

At 402, routine 400 confirms that either TPS of the CCRV or CCRVthrottle are degraded. As an example, either of the components of theCCRV may be determined to be degraded based on routine 300 of FIG. 3. Ifneither component is degraded, at 404 routine 400 may not be performedand may end. However, if degradation has been determined in the CCRV(e.g. either the TPS or the throttle), routine 400 continues to 406where it may determine if the position sensor of the CCRV (specifically,the position sensor of the CCRV throttle) is degraded. For example, theTPS may be determined to be degraded by routine 300 of FIG. 3 based on alack of change in the output of the position sensor when the CCRV iscommanded to a closed position while an increase in TIP is measured inresponse to the command. In another example, the TPS may be determinedto be degraded by routine 300 of FIG. 3 based on a lack of change in theoutput of the position sensor when the CCRV is commanded to an openposition while a decrease in TIP is measured in response to the command.

If yes, routine 400 continues to 408 to deactivate the CCRV throttlesince position control via the position sensor may not be achievable ifthe position sensor is degraded. Thus, the CCRV may be switched off anddeactivated. Alternatively, if the position sensor is degraded, but theCCRV throttle is not, the CCRV throttle may be controlled in anopen-loop manner based on manifold pressure, for example. In this way,greater engine capability is enabled relative to a condition where theCCRV throttle is completely deactivated. Next, at 410, routine 400 mayadjust one or more of a position of the wastegate, the intake throttle,valve timing (e.g. variable cam timing) etc. responsive to thedeactivation of the CCRV and based on existing engine conditions. In oneexample, if surge control is desired, the wastegate may be adjusted to amore open position enabling a reduction in boost levels. Alternatively,an opening of the intake throttle may be adjusted to reduce surgeconditions. In another example, if a higher level of boost is desired,the wastegate may be moved to a more closed position. Airflow may alsobe adjusted by modifying valve timings in the cylinders of the engine.Further still, if the turbocharger in the engine is a variable geometryturbocharger, the controller may adjust the position of the turbineimpeller blades (or vanes) to vary the level of energy that is impartedto the compressor Routine 400 may then end.

If, at 406 it is determined that the position sensor is not degraded inthe CCRV, routine 400 continues to 412 to confirm if the CCRV throttleis degraded and stuck in an open (or mostly open) position. If yes, at414, the wastegate may be adjusted to a more closed position to enable ahigher level of boost when desired. As explained earlier, the CCRV maybleed boost if stuck in an open (or mostly open) position and may affecttorque delivery. Accordingly, the wastegate may be moved to a fullyclosed (or mostly closed) position to direct an entire portion ofexhaust gases to the exhaust turbine of the turbocharger enabling abuildup of boost. If at 412 it is determined that the CCRV throttle isnot stuck open, routine 400 continues to 416 to determine that the CCRVthrottle is stuck closed. Further, at 418, the wastegate may be adjustedto a more open position based on engine conditions. For example, if theCCRV throttle is stuck in a closed (or mostly closed) position, surgecontrol may not be possible. Accordingly, if pressure downstream of theintake compressor(s) increases, the wastegate may be opened to reduceturbocharger speed and charging pressure at the inlet of the intakethrottle. In this way, various actuators may be adjusted differentlywhen the position sensor of the CCRV is determined to be degradedrelative to when the CCRV throttle is determined to be degraded.

Turning now to FIG. 5, it shows example routine 500 illustrating adiagnostic routine to distinguish between degradation of the TPS in theCCRV and degradation of the CCRV throttle. As such, routine 500 may beactivated by a controller based on operator input such as that at adealership, service center, or a repair shop. Further, routine 500 maybe activated by manual command after an initial determination of CCRVdegradation, e.g. at 212 of routine 200.

At 502, the controller may confirm activation of the diagnostic routine.Herein, an operator may activate the diagnostic routine, as in routine500. If confirmation is not received, routine 500 may not be activatedat 504, and may end. However, if confirmation is received at 502,routine 500 progresses to 506 where an input voltage is commanded to theCCRV throttle while TIP is monitored. The input voltage, in one example,may adjust the CCRV throttle to a fully open position from a fullyclosed position. In another example, the input voltage may adjust theCRV throttle to a fully closed position from a mostly open position.Next, at 508, it may be determined if a change in TIP is measured by theTIP sensor. In one example, if the CCRV throttle is moved to the fullyclosed position, an increase in TIP may be measured by the TIP sensor ifthe CCRV throttle is not degraded. If the CCRV throttle is degraded,there may be no increase in TIP upon receiving the input voltage.Alternatively, the measured increase in TIP may not be equal to anexpected rise in TIP responsive to the commanded voltage to close theCCRV throttle if the CCRV throttle is degraded. In another example, adecrease in TIP may be measured if the CCRV throttle is not degraded andis adjusted to an open position. However, if the CCRV throttle isdegraded (e.g. stuck closed), there may be a nominal decrease in TIP.Alternatively, there may be no measurable decrease in TIP if the CCRVthrottle is degraded and stuck closed.

Therefore, at 508, if routine 500 determines that a change in TIP isobserved in response to the input voltage, and that the change in TIP issubstantially equivalent to an expected change, routine 500 continues to510 to determine that the TPS is degraded. However, the measured changein TIP may be due to noise factors such as changes in spark timing,alterations in pedal position, transmission gear changes, etc.Accordingly, routine 500 continues to 512 to confirm the diagnosis ofTPS degradation by activating routine 600 of FIG. 6. In another example,the diagnosis may be deemed complete at 510 and the position sensor ofthe CCRV may be determined to be degraded. At 518, an optionaldiagnostic code indicating TPS degradation may be set and a MIL may beactivated. As such, if engine operation were to continue after thisdetermination of TPS degradation, the CCRV may be deactivated andswitched off.

If at 508, routine 500 determines that there is no change in TIP, it maybe confirmed at 514 that the CCRV throttle is degraded. Alternatively,CCRV throttle may be determined to be degraded if routine 500 confirmsthat the change in TIP is not equivalent to an expected change in TIP.The CCRV throttle may be degraded such that the throttle is stuck in anopen (or mostly open) position. In another example, the CCRV throttlemay be degraded such that it is stuck in a closed (or mostly closed)position. To further confirm the diagnosis that the CCRV throttle isdegraded, routine 500 may proceed to 516 to activate routine 600 of FIG.6. Routine 600 will be further described below. At 518, a diagnosticcode indicating CCRV throttle degradation may be set and the MIL may beactivated.

In this manner, an operator activated routine may be performed todetermine if CCRV degradation is due to degradation of the positionsensor in the CCRV or due to degradation of the CCRV throttle. Bycommanding an input voltage to the CCRV throttle via operator input, amore accurate diagnosis may be made. Further, repairs may be performedin a shorter duration by identifying which of the components of the CCRVis degraded.

FIG. 6 portrays example routine 600 for ensuring that changes in TIP areprimarily due to adjustments in the position of the CCRV throttle.Further, routine 600 may also provide an additional, and more reliable,method for diagnosing degradation in the CCRV throttle. Herein, aperiodic signal may be commanded to the CCRV throttle and correspondingchanges in TIP may be monitored to determine CCRV degradation.

At 602, the CCRV throttle may be diagnosed by commanding a periodicsignal to the CCRV throttle and monitoring changes in TIP responsive tochanges in CCRV throttle position. The periodic signal may bepre-determined and may be commanded by the controller based on operatorinput. Routine 600 may command a periodic signal that has a squarewaveform at 604. Further, at 606, routine 600 includes commanding aperiodic signal that has a periodicity (or period) based on a responsetime of the turbocharger. In one example, the periodicity (or period) ofthe square waveform may be slower than dynamics of the turbocharger. Toelaborate, the period of the square waveform periodic signal may beslower than the response time of the turbocharger. As such, the periodof the square wave may be of sufficient duration to allow theturbocharger and engine system to settle after each edge of the squarewave.

For example, if the CCRV is commanded open by a first edge of theperiodic signal and the CCRV throttle shifts to a more open positionfrom a more closed position, the TIP may decrease initially. In responseto this decrease in TIP, the wastegate may be adjusted by the controllerto a more closed position to return the TIP to a target pressure. Thetarget pressure may be a boost pressure selected for the existing enginecondition. Changes in TIP as a result of adjustments to CCRV throttleposition may, therefore, be transient. Thus, the square waveform mayhave a period that is of adequate duration to enable a re-adjustment ofthe TIP to its target value. It will be appreciated that instead of asquare waveform, a rectangular waveform may be commanded as the periodicsignal.

Returning to routine 600, at 608, it may be determined if observedchanges in TIP substantially correspond to the periodicity of theperiodic signal. For example, it may be determined if the changes in TIPhave a similar frequency and periodic pattern as the commanded periodicsignal to the CCRV throttle. It will be noted that, as explained above,the changes in TIP may be transient such that TIP may initially increase(or decrease) in response to the closing (or opening) of the CCRVthrottle but the TIP may later decrease (or respectively increase) asthe wastegate and/or other actuators are adjusted to restore TIP to thetarget pressure.

If it is determined at 608 that changes in TIP substantially match theperiodic pattern and frequency of the commanded signal to the CCRVthrottle, routine 600 continues to 610 to determine that the CCRVthrottle is not degraded. In essence, the throttle of the CCRV shiftsaccording to the periodic signal command provided to the CCRV throttlefrom the controller.

For example, the square waveform of the periodic signal may alter theposition of the CCRV throttle from a fully open position to a fullyclosed position. Due to the selected period of the square waveform, theCCRV throttle may be maintained in its position of either fully closedor fully open for sufficient duration to enable the change in TIP to berestored to the target pressure. Therefore, if the CCRV throttle is notstuck open (or not stuck closed) and if it shifts according to theperiodic command signal, TIP may change in accordance with the shifts ofthe CCRV throttle. To elaborate, in one example, if the CCRV throttle istransitioned from the fully open position to the fully closed position,TIP may increase significantly at first. Later, the TIP may be reducedto the target value by actuating the wastegate to a more open position.Once the target pressure is attained and the engine and turbochargersystem are settled at a given condition, the periodic signal maytransition the CCRV throttle from the fully closed position to the fullyopen position. In response to this transition, a significant decrease inTIP may be measured initially by the TIP sensor. However, this decreasemay be transient in that the wastegate may be adjusted to a more closedposition to return the TIP to its target value. Thus, at each edge ofthe commanded periodic signal, TIP may change substantially if the CCRVthrottle is not stuck open (or stuck closed). At a later time, TIP maybe restored to the pre-determined target pressure. In one example, anactuator other than the wastegate may be adjusted to return TIP to thetarget pressure, such as the intake throttle and/or valve timing and/orvalve lift. However, such actions may impact engine torque, and requirestill further countermeasures, such as a transmission shift, adjustmentof spark timing, etc.

Optionally, upon establishing that the CCRV is not degraded at 610,routine 600 may continue to 612 to indicate that the position sensor ofthe CCRV is degraded. Herein, the position sensor may be determined tobe degraded based on a prior indication of CCRV degradation such as thatat 212 of routine 200, or prior indication of TPS degradation such as at306 of routine 300, and 510 of routine 500. It will be noted that theprior indications of CCRV degradation and/or TPS degradation may bebased upon a commanded change in CCRV position that does not include aperiodic signal command. Routine 600 may then end.

In another example, upon establishing that the CCRV is not degraded at610, the position sensor of the CCRV may be determined to be degraded ifa commanded change in CCRV position at a later time, followingdetermining CCRV throttle robustness, does not produce a correspondingchange in the response of the position sensor.

On the other hand, if it is confirmed at 608 that changes in TIP do notsubstantially correspond to the periodic pattern and frequency of thecommanded signal to the CCRV throttle, routine 600 continues to 614 todetermine that the CCRV throttle is degraded. Herein, the throttle ofthe CCRV may not shift according to the periodic signal command providedto the CCRV throttle from the controller. Accordingly, the CCRV throttlemay be lodged in a fully open, fully closed, or a positionthere-between. At 616, routine 600 may optionally indicate a respectivediagnostic code indicating a stuck CCRV throttle (stuck open or stuckclosed) to the operator and the MIL may be actuated.

Thus, an example system may comprise an engine, a turbocharger forproviding a boosted aircharge to the engine, the turbocharger includingan exhaust turbine and an intake compressor, an intake throttlepositioned in an intake passage downstream of the intake compressor, awastegate coupled across the turbine, a continuously variablerecirculation valve (CCRV) coupled across the compressor, the CCRVincluding a CCRV throttle and a CCRV position sensor, a throttle inletpressure (TIP) sensor coupled to the intake passage upstream of theintake throttle and downstream of the intake compressor. The examplesystem may further comprise a control system with computer-readableinstructions stored on non-transitory memory for commanding a periodicsignal to the CCRV, measuring changes in pressure at an inlet of theintake throttle via the TIP sensor, and if the changes in pressure atthe inlet of the intake throttle in response to the commanded periodicsignal do not correspond to a frequency of the commanded periodicsignal, indicating degradation of the CCRV throttle. The control systemmay include further instructions for, if the changes in pressure at theinlet of the intake throttle in response to the commanded periodicsignal substantially correspond to the frequency of the commandedperiodic signal, not indicating degradation of the CCRV throttle.

Further still, the control system may include additional instructionsfor indicating degradation of the CCRV position sensor based on a firstdetermination of degradation of the CCRV, and the changes in pressure atthe inlet of the intake throttle in response to the commanded periodicsignal substantially corresponding to the frequency of the commandedperiodic signal. The first determination of degradation of the CCRV mayinclude a diagnosis such as that made at 212 in routine 200. Therefore,the first determination of degradation of the CCRV may include a lack ofchange in an output of the CCRV position sensor responsive to a firstcommanded change in position of the CCRV (such as that at 206 in routine200), the first commanded change being distinct from the periodicsignal. Alternately, the first determination of degradation of the CCRVmay include the determination of degradation of the TPS sensor at 510 inroutine 500 followed by a confirmation in routine 600. Herein, if theposition sensor is determined to be degraded in routine 500, routine 600may confirm this diagnosis of TPS degradation when changes in TIPcorrespond substantially to the periodic signal commanded to the CRVthrottle. It will be noted that in both cases (whether routine 500 orroutine 200), the first commanded change in position of the CCRV isdistinct from the periodic signal command. Further, the first commandedchange in position may not be a periodic signal command. The periodicsignal may include a square waveform with a period based on responsetime of the turbocharger. Alternatively, the periodic signal may includea rectangular waveform with a period based on response time of theturbocharger. Furthermore, the control system may include furtherinstructions for, deactivating the CCRV and adjusting one or more of thewastegate, a position of the intake throttle, and valve timing upondeactivating the CCRV in response to the indication of degradation ofthe position sensor of the CCRV.

FIG. 7 depicts an example comparison of identification of degradation ofthe position sensor of the CRV relative to that of the CRV throttle inan example engine system such as that of FIG. 1. Map 700 of FIG. 7 showsCCRV throttle degradation at plot 702, CCRV position sensor (TPS)degradation at plot 704, output from CCRV position sensor (TPS) at plot708, TIP as measured by the TIP sensor at plot 710, and CCRV command atplot 712. All the above are plotted against time on the x-axis. Further,time is depicted increasing from left to right along the x-axis. It willbe noted that map 700 presents three separate degradation determinationsat three distinct events.

Prior to t1, the CCRV may be maintained at a fully open position asdemonstrated by the command to the CCRV. TIP as measured by the TIPsensor (plot 710) is lower since the CCRV is at the fully open position.Further, the output of the TPS indicates that the CCRV throttle is atthe open position. At t1, the controller may command a change inposition of the CCRV. As shown at t1, the CCRV may be commanded to afully closed position from the fully open position existing prior to t1.The output of the TPS, in response to this command at t1, does notchange and the TPS continues to depict the CCRV (or CCRV throttle) inits open position. However, an increase in TIP is measured between t1and t2 indicating that the position of the CCRV throttle hastransitioned from the fully open position to the fully closed.Accordingly, at t2, degradation of the position sensor of the CRV inindicated (plot 704) while plot 702 shows that there is no degradationof the CCRV throttle. Thus, the controller may indicate degradation ofthe position sensor based on an increase in throttle inlet pressure inresponse to the CCRV being commanded to a closed position and feedbackfrom the position sensor indicating the CCRV is open.

Between t2 and t3, a duration of time may elapse wherein the positionsensor of the CRV may be repaired or replaced such that at t3 theposition sensor functions in a substantially robust manner. At t3, theengine may be operational with the CCRV in a mostly open position ascommanded (plot 712). Further, the TPS indicates that the CCRV throttleis mostly open and TIP may be lower at t3 due to the CCRV being at themostly open position.

At t4, the CCRV (and the CCRV throttle) may be commanded closed to thefully closed position. For example, a higher level of boost may bedemanded due to a rise in torque demand resulting in the CCRV beingcommanded to the fully closed position. As will be observed, TIP doesnot rise as would be expected if the CCRV throttle had closed (plot710). Herein, a peak TIP may be expected due to the CCRV being commandedto the fully closed position. The observed rise in TIP, though, isnominal while the TPS output undergoes no change and may indicate thatthe CCRV throttle continues at its open position. In one example, TPSmay indicate a partially open/partially closed position of the CCRVthrottle, although the signal-to-noise ratio may be smaller when theCCRV is stuck closer to the desired position. When stuck farther fromdesired position, degradation may be more quickly identified andindicated. Therefore, at t5, the CCRV throttle may be determined to bedegraded based on the lack of change in response of the position sensorand substantially no change in TIP in response to the commanded changein position of the CCRV throttle. The CCRV throttle may be stuck openand boost may not increase sufficiently. In response to thisdetermination of the CCRV throttle being stuck open, the controller mayadjust the wastegate to a fully closed position to provide higher levelsof boost.

Between t5 and t6, adequate time may pass to repair the CCRV throttlesuch that the throttle is dislodged from its stuck position. At t6, theengine may be operating with the CCRV (and the CCRV throttle) in a fullyclosed position. TPS output indicates that the CCRV throttle is closedand TIP is higher, possibly at peak TIP, indicating the same. At t7, thecontroller may command a change in position of the CCRV throttle fromthe fully closed position to the fully open position. However, there maybe no change in TIP in response to this command (plot 710) and the TPSoutput (plot 708) may not indicate a change in the position of the CCRV.As such, the CCRV throttle may be stuck closed. Therefore, at t8, CCRVdegradation may be indicated while the TPS is depicted as robust. Thus,the controller may indicate degradation of the CCRV throttle based on alack of change in throttle inlet pressure in response to the CCRV beingcommanded to an open (or fully open) position, and feedback from theposition sensor indicating that the CCRV is closed.

Thus, an example system may comprise an engine, a turbocharger forproviding a boosted aircharge to the engine, the turbocharger includingan exhaust turbine and an intake compressor, an intake throttlepositioned in an intake passage downstream of the intake compressor, awastegate coupled across the turbine, a continuously variablerecirculation valve (CCRV) coupled across the compressor, the CCRVincluding a CCRV throttle and a CCRV position sensor, a throttle inletpressure (TIP) sensor coupled to the intake passage upstream of theintake throttle and downstream of the intake compressor. The examplesystem may further comprise a control system with computer-readableinstructions stored on non-transitory memory for actuating a change inposition of the CCRV, determining degradation of the CCRV based onfeedback from the CCRV position sensor indicating the CCRV throttle didnot change position in response to the actuating, and during a firstcondition, indicating degradation of the CCRV position sensor, andduring a second condition, indicating degradation of the CCRV throttle.The first condition may include an expected change in throttle inletpressure measured by the throttle inlet pressure sensor in response tothe actuating, and wherein the second condition may includesubstantially no change in throttle inlet pressure measured by thethrottle inlet pressure sensor. The control system may include furtherinstructions for deactivating the CCRV in response to the determining ofdegradation of the CCRV, and for adjusting one or more of the wastegate,the intake throttle, and valve timing in response to the deactivating ofthe CCRV.

Turning now to FIG. 8, it displays map 800 portraying an examplediagnosis of the CCRV throttle in an example engine system such asengine system 100 of FIG. 1, based on a periodic signal command. Thisexample diagnosis using the periodic signal command may reduce noise inTIP from other factors such as changes in spark timing, pedal position,gear, etc.

Map 800 includes CCRV throttle degradation at plot 802, CCRV positionsensor (TPS) degradation at plot 804, indication of CCRV degradation (asa whole unit) at plot 806, output from CCRV position sensor (TPS) atplot 808, TIP as measured by the TIP sensor at plot 810, and CCRVcommand at plot 812. All the above are plotted against time on thex-axis. Further, time is depicted increasing from left to right alongthe x-axis. Line 811 represents a target throttle inlet pressure thatthe engine may be operating at during the determination of CCRVdegradation.

Prior to t1, the engine may be operated by a user away from adealership, service center, repair shop, etc. in an everyday manner.Further, the engine may be operating with the CCRV (and CCRV throttle)in a fully open position. This position of the CCRV throttle isindicated by the TPS output. TIP may not be actively monitored for CCRVdiagnosis until a likelihood of CCRV degradation (such as at 212 ofroutine 200) is indicated. Therefore, TIP may not be measured inresponse to the CCRV command until t3. At t1, the CCRV may be commandedto a fully closed position. However, TPS response indicates that thereis no change in CCRV throttle position at t1 in response to thecommanded change in CCRV throttle position. Accordingly, at t2, thecontroller may indicate that the CCRV is likely degraded. In oneexample, this may be recorded as a first determination of degradation ofthe CCRV.

In response to the indication of CCRV degradation, determination of CCRVcomponent specific degradation may be initiated at t3 by operator inputat the dealership, service center, or repair shop. As will be noted, aduration of time may elapse between detection of CCRV degradation at t2and component specific diagnosis at t3. For example, between t2 and t3,while the engine is operated by the user, the controller may attempt todistinguish between degradation of the CCRV throttle and the CCRVposition sensor (e.g. via routine 300 of FIG. 3). In this example, theexample diagnosis depicted after t3 may be performed to confirm aprevious diagnosis of likely degradation.

Between t3 and t4, the engine may be operating with a TIP that issubstantially similar to a target TIP (line 811) with the CCRV at thefully open position. As such, target TIP with the CCRV at fully openposition may be achieved by adjusting the opening of the intake throttlelocated downstream of the intake compressor and/or by adjusting theopening of the wastegate.

At t4, a periodic signal in the form of a square waveform may becommanded to the CCRV throttle as shown in plot 812. Further, variationsin TIP may be monitored (plot 810) in response to this periodic signal.As shown in plot 810, changes in TIP substantially follow a similarfrequency and periodic pattern as the commanded periodic signal to theCCRV between t4 and t9. The commanded periodic signal may have asufficiently slow period that ensures adequate time is available forturbocharger response. Further, each change in position of the CCRVthrottle results in a change in TIP that may be transient. To elaborate,at t4, the periodic signal may command adjusting the CCRV to the fullyclosed position. If the CCRV throttle responds to this command (and isnot degraded) and transitions to the fully closed position, asubstantial increase in TIP (above target TIP of line 811) may beobserved at t4 in response to the transition. However, since the targetTIP is lower than this increased level of TIP, the wastergate may beadjusted to a more open position to decrease TIP. Alternatively, theopening of the intake throttle may be increased to reduce TIP.Accordingly, TIP reduces to the target pressure (line 811) at t5 beforethe periodic signal commands a change in CCRV position at t6. Thus, theperiod of the periodic signal may be sufficient to allow restoring TIPto the target pressure and maintain turbocharger dynamics.

At t6, the periodic signal commands a change in position of the CCRVfrom fully closed to fully open. In response to this command, the CCRVthrottle may be adjusted to the fully open position (if not degraded)resulting in a considerable drop in TIP at t6. In response to this dropin TIP, the wastegate may be adjusted to a more closed position toincrease TIP to its target pressure value. Alternatively, the intakethrottle may be moved to a more closed position from a more openposition to increase TIP. As observed, TIP attains the target pressureat t7 and at t8, the periodic signal may command a change in position ofthe CCRV from fully open to fully closed. The cycle may repeat itselfuntil a sufficient number of transitions are observed. In the exampleshown, four transitions may be sufficient to determine whether the CCRVthrottle is degraded or robust. In the example shown, the CCRV throttleis determined to be robust (and not degraded) since the changes in TIPsubstantially correspond to the frequency and pattern of the commandedperiodic signal. Therefore, at t9, the controller may indicate that theTPS is degraded while the CCRV throttle is indicated as not degraded. Assuch, degradation of the TPS is based upon the first determination ofCCRV degradation at t2 and the subsequent confirmation by applying theperiodic signal.

Thus, an example method for a boosted engine may comprise commanding aperiodic signal to a compressor bypass valve (CBV), and indicatingdegradation of a throttle of the CBV based on changes in pressure at aninlet of an intake throttle in response to the periodic signal. Thepressure at the inlet of the intake throttle may be measured by a sensorcoupled to an intake passage and located upstream of the intake throttleand downstream of an intake compressor of the boosted engine, such asTIP sensor 173 of FIG. 1. The periodic signal may be commanded by acontroller of the boosted engine based on operator input. The periodicsignal may include a square waveform, and the periodic signal may have aperiodicity (or period) based on response time of a turbocharger of theboosted engine. The method may indicate degradation of the throttle ofthe CBV when changes in pressure at the inlet of the intake throttle donot substantially correspond to the periodicity of the periodic signalto the CBV. The method, on the other hand, may indicate degradation of aposition sensor of the CBV when changes in pressure at the inlet of theintake throttle substantially correspond to the periodicity of theperiodic signal, and when a second commanded change in a position of thethrottle of the CBV does not produce a corresponding change in aresponse of the position sensor. The second commanded change may not bea periodic signal. The method may comprise deactivating the CBV inresponse to the indicating of degradation of the position sensor of theCBV. The method may further comprise adjusting one or more of awastegate, the intake throttle, and variable cam timing responsive tothe deactivating of the CBV. The CBV may be a continuously variablecompressor bypass valve.

Another example method for a boosted engine may comprise commanding aperiodic signal command to a compressor recirculation valve (CRV)comprising a square waveform, and distinguishing between degradation ofa position sensor of the CRV and a throttle of the CRV based on changesin pressure at an inlet of an intake throttle in response to the squarewaveform periodic signal command. The periodic signal command may have aperiod slower than a response time of a turbocharger in the boostedengine, and the throttle of the CRV may be determined to be degradedwhen the changes in pressure at the inlet of intake throttle in responseto the periodic signal command do not substantially correspond to theperiodicity of the periodic signal. The position sensor of the CRV maybe determined to be degraded when changes in pressure at the inlet ofthe intake throttle substantially correspond to the periodicity of theperiodic signal command to the CRV, and when a second commanded changein a position of the throttle of the CRV does not produce acorresponding change in a response of the position sensor, the secondcommanded change being distinct from the periodic signal command.

In this way, degradation of the CCRV throttle may be differentiated fromdegradation of the position sensor of the CCRV. Specific componentdegradation may be identified by simply monitoring TIP and the output ofthe position sensor in the CRV in response to a command to the CRV bythe controller. Thus, additional sensors for determining degradation inthe CRV may not be needed. Further, component specific degradation maybe more accurately identified by commanding a periodic signal command tothe CCRV. Accordingly, repair of the CCRV may occur with lower expensesand within a shorter duration. Overall, engine maintenance may be morereliable and costs may be reduced.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method for a boosted engine, comprising:sending, via an electronic controller, a periodic signal command to acompressor recirculation valve (CRV) comprising a square waveform;distinguishing between degradation of a position sensor of the CRV and athrottle of the CRV based on changes in pressure at an inlet of anintake throttle in response to the square waveform periodic signalcommand; and in response to the degradation of the throttle of the CRV,adjusting a position of a wastegate valve.
 2. The method of claim 1,wherein the periodic signal command has a period slower than a responsetime of a turbocharger in the boosted engine, and wherein the throttleof the CRV is determined to be degraded when the changes in pressure atthe inlet of the intake throttle in response to the periodic signalcommand do not correspond to a periodicity of the periodic signalcommand.
 3. The method of claim 2, wherein the position sensor of theCRV is determined to be degraded when the changes in pressure at theinlet of the intake throttle correspond to the periodicity of theperiodic signal command to the CRV, and when a second signal commandinga change in a position of the throttle of the CRV does not produce acorresponding change in a response of the position sensor, the secondsignal being distinct from the periodic signal command.
 4. A method foroperating a boosted engine, comprising: sending, with an electroniccontroller, a periodic actuator signal to a compressor bypass valve(CBV) actuator; indicating degradation of a throttle of a CBV byactivating a diagnostic code stored in memory of the electroniccontroller based on changes in pressure at an inlet of an intakethrottle in response to the periodic actuator signal; deactivating theCBV with the electronic controller in response to an indication ofdegradation of a position sensor of the CBV; and adjusting a position ofa wastegate valve in response to the degradation of the throttle of theCBV.
 5. The method of claim 4, wherein pressure at the inlet of theintake throttle is measured by a sensor coupled to an intake passage andlocated upstream of the intake throttle and downstream of an intakecompressor of the boosted engine.
 6. The method of claim 5, wherein theperiodic actuator signal is sent based on an operator input.
 7. Themethod of claim 6, wherein the periodic actuator signal includes asquare waveform.
 8. The method of claim 5, wherein the periodic actuatorsignal has a periodicity based on response time of a turbocharger of theboosted engine.
 9. The method of claim 8, further comprising indicatingdegradation of the throttle of the CBV when changes in pressure at theinlet of the intake throttle do not correspond to the periodicity of theperiodic actuator signal to the CBV, including a determination ofwhether changes in throttle inlet pressure result in shifts in positionof the CBV throttle.
 10. The method of claim 8, further comprisingindicating degradation of the position sensor of the CBV when changes inpressure at the inlet of the intake throttle correspond to theperiodicity of the periodic actuator signal, and when sending a secondactuator signal commanding a change in a position of the throttle of theCBV does not produce a corresponding change in a response of theposition sensor.
 11. The method of claim 10, wherein the second actuatorsignal is not a periodic signal.
 12. The method of claim 4, furthercomprising adjusting the intake throttle responsive to the deactivatingof the CBV.
 13. The method of claim 4, wherein the CBV is a continuouslyvariable compressor bypass valve.
 14. A system, comprising; an engine; aturbocharger for providing a boosted aircharge to the engine, theturbocharger including an exhaust turbine and an intake compressor; anintake throttle positioned in an intake passage downstream of the intakecompressor; a wastegate coupled across the exhaust turbine; acontinuously variable recirculation valve (CCRV) coupled across theintake compressor, the CCRV including a CCRV throttle and a CCRVposition sensor; a throttle inlet pressure (TIP) sensor coupled to theintake passage upstream of the intake throttle and downstream of theintake compressor; and a control system with computer-readableinstructions stored on non-transitory memory for: commanding a periodicsignal to the CCRV; measuring changes in pressure at an inlet of theintake throttle via the TIP sensor; and if the changes in pressure atthe inlet of the intake throttle in response to the commanded periodicsignal do not correspond to a frequency of the commanded periodicsignal, indicating degradation of the CCRV throttle and adjusting aposition of a wastegate valve in response to the degradation of the CCRVthrottle.
 15. The system of dam 14, wherein the control system includesfurther instructions for, if the changes in pressure at the inlet of theintake throttle in response to the commanded periodic signal correspondto the frequency of the commanded periodic signal, not indicatingdegradation of the CCRV throttle.
 16. The system of claim 15, whereinthe control system includes additional instructions for indicatingdegradation of the CCRV position sensor based on a first determinationof degradation of the CCRV, and the changes in pressure at the inlet ofthe intake throttle in response to the commanded periodic signalcorresponding to the frequency of the commanded periodic signal.
 17. Thesystem of claim 16, wherein the first determination of degradation ofthe CCRV includes a lack of change in an output of the CCRV positionsensor responsive to a first commanded change in position of the CCRV,the first commanded change being distinct from the periodic signal. 18.The system of claim 17, wherein the periodic signal includes a squarewaveform with a period based on response time of the turbocharger. 19.The system of claim 18, wherein the control system includes furtherinstructions for, deactivating the CCRV and adjusting, a position of theintake throttle in response to deactivating the CCRV.